In the prior art, liquid dispensers have been designed to respond to a user request for an amount of liquid by dispensing the requested amount. Such dispensers may achieve processor controlled dispensing by providing the processor with a signal indicating the amount of liquid remaining in the reservoir. The greater the amount of remaining liquid, the faster the liquid will dispense out of a reservoir outlet.
For example, Australian Patent No. 728683 to Pascoe (“Pascoe”) describes a dispenser with a liquid reservoir that is supported by a load cell. The load cell is strained in response to the remaining liquid in the reservoir and continuously sends signals regarding the detected weight to a processor. Upon receiving the request for an amount of liquid, the processor controls the opening and closing of the valve. In this manner, each time the dispenser is asked to dispense a requested amount of liquid, the dispenser may obtain the output of the load cell and control the valve, leaving the valve open for a period suitable to dispense the requested amount.
Prior art dispensers may use formulas to determine the open valve time, and manufacturers may determine the formulas based on dispense data collected during testing or calibrating of their equipment. Methods for controlling the dispensing of liquid are described in Chinese Patent Publication No. 101446833 to Wang (“Wang”). Wang describes such calibration by filling the reservoir of a dispenser with a predetermined amount of liquid, positioning a container on a scale and under the dispenser's valve, and opening the valve to drain the liquid from the reservoir, while measuring the times and weights of the liquid dispensed. In this manner, Wang obtains data about the flow rate based on the amount of remaining liquid and fits the data to match a mathematical formula. From this formula, Wang derives another formula for the open valve time to dispense a requested amount of liquid, based on the amount of remaining liquid. Another example of a liquid dispenser may be found in U.S. Pat. No. 8,534,497 to Veltrop (“Veltrop”).
In this manner, liquid dispensers in the prior art may be equipped with load cells that measure the remaining amount of liquid in the dispenser's reservoir. When a dispenser receives a user request for a requested amount of liquid, the dispenser may obtain the output of the load cell supporting the liquid reservoir and determine an open valve time to dispense that amount.